Top: photospheric abundances of BD−22°3467 compared with solar values (Asplund et al. 2009), and mean values from three objects of Good et al. (2005, blue triangles) that are located within the error ellipse (cf. Fig. 15, green squares there). Arrows indicate upper limits. Bottom: comparison of number ratios compared with predictions of diffusion calculations for hydrogen-rich (DA-, blue squares) and helium-rich (DO-type, green triangles) WDs (Chayer et al. 1995a,b) with T_eff = 80   kK and log g = 7.2.